The invention relates to automatic manufacture of receptacles having thin walls such as various sorts of boxes, pots and cups.
These receptacles are generally formed from sheets of plastics material of metal sheets, greaseproof paper or, very frequently, complex products such as liminates of paper, aluminum and polyethylene. They comprise, very generally three elements that is:
A body defined by a wall of the receptacle, which may be shaped, for example, as a trunk of a cone, a cylinder, trunk of a pyramid or prism,
A curved bottom at one end of the body of which the concavity may be directed towards the inside or the outside,
A cover provided with a simple upper wall edge at the other end of the body; the wall edge may be formed by an associated element but also by a part attached to the upper edge of the body; it is generally intended to give to the receptacle a sufficient rigidity and possibly to receive a cover or lid.
Even if the receptacles are not formed by rotation about an axis it is possible to assign to the body a longitudinal axis which is generally perpendicular to the bottom of the receptacle.
According to the composition of the materials which are used in the manufacture of the receptacle, the elements may be joined by adhesion, welding, brazing or even by press-fitting. Possible processes used for welding include, in particular, welding by the Joule effect, by ultrasonics or by dielectric loss heating at high frequency.
As a general rule, the successive stages of manufacture are carried out in different machines between which the part-finished receptacles are transferred, optionally automatically by mechanical members which are moved in a plane perpendicular to the axis of the receptacles for transporting the receptacles to successive work stations.
It is known, in particular, to roll on a preformed bottom a blank of convenient shape, to join the blank to the bottom while closing the blank by welding to form the body then to finish the upper edge of the receptacle by pressing either at a low or high temperature.
In general, the tools used at different working stations comprise essentially two complementary members situated on the same axis corresponding to that of the receptacle and intended to be positioned on either side of the wall to be operated on, that is:
A female member formed generally of at least two jaws surrounding the exterior of the body and a male organ penetrating inside the opening of the latter.